Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2003-02-03
2004-06-22
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S011000
Reexamination Certificate
active
06752482
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a jetting head capable of ejecting various kinds of liquid in the form of droplets for use in an ink jet printer, a display manufacturing apparatus, an electrode forming apparatus, a biochip manufacturing apparatus, etc., and more particularly, to a jetting apparatus having a plurality of flexible flat cables to be used for supplying drive signals from a head driver to a jetting head.
As a jetting apparatus having a jetting head capable of ejecting liquid in the form of a liquid droplet, for example, there has been proposed an ink jet printer in which ink droplets are ejected to record an image or the like on recording paper, an electrode forming apparatus in which an electrode material in a liquid form is ejected onto a substrate to thereby form electrodes, a biochip manufacturing apparatus in which biological samples are ejected to manufacture biochips, or a micropipette for ejecting a predetermined amount of a sample into a vessel.
For instance, in an ink jet printer employing piezoelectric elements as drive elements for ejecting ink, a plurality of piezoelectric elements, which are provided so as to correspond to a plurality of nozzles of a print head, are selectively activated, whereby ink droplets are ejected from the nozzles in accordance with the dynamic pressure generated by the respective piezoelectric elements. Dots are formed on recording paper by causing the ink droplets to adhere to the recording paper, thus effecting printing operation.
Here, the piezoelectric elements are provided so as to correspond to nozzles to be used for ejecting ink droplets. The piezoelectric elements are actuated by a drive signal supplied from a head driver mounted in the print head, thereby ejecting ink droplets.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a device and a method for driving a jetting head designed to readily retain predetermined bias voltages of respective piezoelectric elements through use of a simple, compact configuration and at low cost.
In order to achieve the above object, according to the invention, there is provided a head driving device, which drives a plurality of pressure generating elements for generating pressure fluctuation in a jetted object contained in each of associated pressure chambers formed in a jetting head of a jetting apparatus to eject the jetted object from each of nozzles communicated with the associated pressure chambers, the head driving device comprising:
a head driver, which generates a drive signal which is selectively applied to at least one of the pressure generating elements to be driven; and
a bias potential provider, which selectively applies a bias potential to at least one of the pressure generating elements not to be driven.
In such a configuration, the non-actuated pressure generating elements are held at the bias potential. Accordingly, the voltage applied to both electrodes of the non-actuated pressure generating elements becomes substantially zero. Hence, power draw is reduced, and a voltage drop stemming from spontaneous discharge of the pressure generating elements becomes smaller. Hence, a power loss is diminished.
Further, occurrence of discharge due to a potential difference between pressure generating elements to be driven and pressure generating elements not to be driven is also reduced. In addition, a further increase in arrangement density of a head can be attained without involvement of an operation for providing insulation between the electrodes of the pressure generating elements.
Preferably, the bias potential is a reference potential of the drive signal.
Preferably, the bias potential provider includes a potential applier which applies the bias potential, and a charger which charges the potential applier with a drive potential of the drive signal.
Here, it is preferable that the charger includes a transistor which applies the drive potential to the potential applier, and a switcher which supplies the drive signal to a base terminal of the transistor during a time period in which the drive signal deactivates the pressure generating elements.
In such a configuration, the transistor is turned on by the supplied drive signal to charge the potential applier with the bias potential.
Here, it is further preferable that the switcher continuously supplies the drive signal before and after a jetting operation is performed.
Specifically, the drive signal is supplied to discharge the potential applier after the jetting operation is performed.
Before the jetting operation, since the potential applier is gradually charged to reach the bias potential by the continuous supply of the drive signal, there is prevented occurrence of faulty operations of respective pressure generating elements, which would otherwise be caused by a sudden increase in the potential of the ground-side electrodes before commencement of the jetting operation.
After the jetting operation, since the potential applier is gradually discharged by the continuous supply of the drive signal, there is prevented occurrence of faulty operations of the respective pressure generating elements, which would otherwise be caused by a sudden drop in the voltage of the ground-side electrodes after completion of the jetting operation.
Further, it is preferable that: the head driver is mounted on the jetting head, and the switcher is embodied by a part of a switching circuit included in the head driver which selectively applies the drive signal to the at least one pressure generating elements to be driven.
In such a configuration, the switcher is provided by utilizing a surplus unused section of an existing switching circuit of the head driver mounted on a jetting head, thereby curtailing the cost of parts. Further, a space to be used for mounting the switcher is not particularly required, thus rendering the apparatus compact.
According to the invention, there is also provided a method of driving a jetting head provided with pressure generating elements, the method comprising steps of:
generating a drive signal selectively applied to at least one of the pressure generating elements to be driven to eject jetted objects; and
applying a bias potential from a potential applier to at least one of the pressure generating elements not to be driven.
Preferably, the driving method further comprises a step of charging the potential applier with a drive potential of the drive signal.
Here, it is preferable that the charging step is performed during a time period in which the drive signal deactivates the pressure generating elements.
It is further preferable that the charging step is performed during a time period in which the drive signal deactivates the pressure generating elements.
According to the invention, there is also provided a head driving device, which drives a plurality of pressure generating elements for generating pressure fluctuation in a jetted object contained in each of associated pressure chambers formed in a jetting head of a jetting apparatus to eject the jetted object from each of nozzles communicated with the associated pressure chambers, the head driving device comprising:
a head driver, which generates a drive signal which is selectively applied to at least one of the pressure generating elements to be driven;
a bias potential provider, which applies a bias potential to respective ground-side electrodes of the pressure generating elements; and
an IC package, in which the head driver and the bias potential provider are provided.
In such a configuration, the ground-side electrodes of the pressure generating elements are held at the bias potential.
Accordingly, the voltage to be applied across both electrodes of the pressure generating elements is reduced. Therefore, power consumption is diminished, and a voltage drop stemming from spontaneous discharge of the pressure generating elements is small, thereby reducing a power loss.
Further, since the voltage to be applied to the pressure generating elements becomes relatively low, electric discharge stemming from a voltage differ
Fukano Takakazu
Tamura Noboru
Dudding Alfred
Meier Stephen D.
Seiko Epson Corporation
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